This invention relates to an automatic document feeder and more particularly it relates an automatic document feeder for use with an image forming apparatus, such as a copying machine or facsimile system, which forms images corresponding to document images, said feeder being designed not only for manual setting of documents on the document platen but also for automatic setting of documents.
In copying machines which have heretofore been in wide use, the operator performs a copying operation by first upwardly turning the document hold-down platen which covers the upper surface of the document platen to set a document at a predetermined position on the document platen, and then restoring the document hold-down platen to hold the document between the document platen and the document hold-down platen, whereupon he actuates the copying machine for copying operation.
Thus, the upward turning and restoration of the hold-down platen must be effected for each exchange of documents and involve the creation of an air pressure which often causes the inconvenience of the document deviating from the predetermined position to the extent of leading to a failure in providing a desired document image at a desired position; for example, the document image is formed at an off-center position on the copying paper sheet or only part of the document image is formed on the copying paper sheet. Further, since the document hold-down platen must be turned for each exchange of documents, the operation is complicated, which is another inconvenience. On the other hand, there is an advantage that even if the documents are different in thickness, they can be set with ease.
In recent years, for automatic setting of documents, there has been provided a copying machine with a document feeder installed above the document platen.
With such copying machine, the labor of setting a document can be greatly reduced, but for the time taken for the copying-ready state to be established after the power for the copying machine is turned on, (e.g., for the time required for the fixing heat roller to be heated to a predetermined temperature set as the fixation temperature) the operator has to stand by in front of the copying machine, a fact which reduces the efficiency of copying work and hence the efficiency of the overall office work including copying work.
Further, with consideration given to the advantages of the aforesaid two types of copying machines, there has been provided a copying machine with the document feeder adapted to turn upwardly with respect to the document platen. With this machine, however, after a document has been manually set, if other documents are to be automatically set by the document feeder, this will sometimes result in an inconvenience; since the manually set document, whether thin or thick, will be automatically discharged, if it is a thick one, then the discharge rollers can be damaged or jammed with the thick document. Another inconvenience is that although an automatically set document is automatically discharged upon completion of image forming operation, the manually set document will stay forever on the document platen unless it is removed by the operator.
Further, in such image forming apparatus as the facsimile system, if the same document feeder as in the aforesaid copying machine is used, the same inconveniences as described above will occur.
An object of this invention is to provide an arrangement wherein upon the lapse of the time required for the image forming apparatus to be ready for image forming operation (hereinafter referred to as the warm-up time), document feed is automatically effected so that an image forming operation for at least the first document can be automatically performed while the operator, away from the image forming apparatus, is doing another job.
Another object of the invention is to actuate the automatic document feeder only when there is a document set in the copying machine.
Another object of the invention is to ensure that in discharging a document, the discharge section does not get damaged or jammed with the document.
Another object of the invention is to prevent the automatic document feeder from being damaged or jammed with a document without decreasing the speed at which a document is set by the automatic document feeder.
A further object of this invention is to indicate the damage preventing state and document jam preventing state of the document feed section to the operator.
Another object of the invention is to provide an arrangement wherein when a document is manually set, if the operator forgets to remove the document, this situation is noticed to the operator to remind him of having forgotten to remove the document.
This invention provides an automatic document feeder which is upwardly turnable with respect to the document platen and which, after transferring a document to a predetermined position, discharges the document, said feeder having mode discriminating means for discriminating between manual and automatic document setting modes, document detecting means for detecting the presence or absence of a document at a predetermined position, and control means for driving the automatic document feeder with a predetermined timing.
The automatic document feeder may have a motor of its own for document transfer or a power transmission mechanism which transmits the driving force of the prime mover section of the image forming apparatus itself only when the automatic document setting mode is selected. The mode discriminating means may be of a type which discrminates modes as by keying operation on the document feeder or of a type which discriminates modes on the basis of whether or not a turning operation is applied to the automatic document feeder. As for the document detecting means, it is generally of the optical type using photelectric elements for detection, but it may be of the mechanical type using limit swtiches or the like. Further, the control means may be an electric circuit which controls the timing and duration with which the motor is operated or it may be another electric circuit which controls the timing and duration with which a solenoid clutch forming a portion of the drive force transmission mechanism is operated.